Semiconductor device and manufacturing method of the same

ABSTRACT

A semiconductor device includes a plurality of electrode layers provided at designated positions of a semiconductor substrate, an organic insulation film formed on the semiconductor substrate by selectively exposing designated areas of the electrode layers, and projection electrodes for outside connection, the projection electrodes being formed on the designated areas of the electrode layers. Thickness of the organic insulation film situated in the vicinity of the periphery of the projection electrodes is greater than thickness of the organic insulation film situated between the projection electrodes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to semiconductor devices andmanufacturing methods of the same, and more specifically, to asemiconductor device having a projection electrode (bump) for outsideconnection and an organic insulation film and a manufacturing method ofthe same.

2. Description of the Related Art

Recently, a flip chip connection structure using a projection electrodefor outside connection, called a bump, has been widely applied for highdensity mounting of a package and a semiconductor element.

In a case where solder is selected as a material of such a bump, thebump can be formed by a plating method or a printing method.

A barrier metal layer is formed on the electrode layer by using anelectrolytic plating method in order to prevent the solder from beingdiffused on the semiconductor element, and the soldering bump is formedon the barrier metal layer by a plating method. See Japanese Laid-OpenPatent Application Publications No. 2004-200420 and No. 9-191012, forexample.

In this case, a surface of the semiconductor element is covered with anorganic insulation film such as polyimide for device protection. Thesurface of the electrode layer is also selectively covered with theorganic insulation film.

A manufacturing process of the bump by using the relating art platingmethod in a manufacturing process of the semiconductor device is shownin FIG. 1.

In a bump forming process by using the related art plating method,first, as shown in FIG. 1-(a), a wiring layer made of silicon (Si) andan electrode layer (electrode pad) 3 are provided on an upper surface,namely a circuit element forming surface, of a semiconductor substrate 1made of silicon (Si) via an insulation film (insulation layer) made ofsilicon oxide, for example.

An upper part of the semiconductor substrate 1 including the wiringlayer and the electrode layer 3 is covered with an inorganic insulationfilm (passivation film) 2 made of silicon nitride (SiN) or the like.

In addition, an organic insulation film 4 such as a polyimide resinlayer or the like is provided on the inorganic insulation film 2. Theorganic insulation film 4 is formed for surface protection of thesemiconductor element and for easing stress concentrated on a base ofthe bump 9 when the semiconductor element is mounted on a wiring board11 (See FIG. 3).

An opening is formed in the inorganic insulation film 2 and the organicinsulation film 4 as corresponding to an expected forming position onthe electrode layer 3 of the soldering bump 9 so that a pad is exposed.

Illustration of an active element such as a transistor, and a passiveelement such as resistor element or capacity element formed on thesemiconductor substrate 1, an isolation area for insulation-isolatingbetween these elements, an interlayer insulation layer, an inter-elementmutual wiring layer, or the like is omitted in FIG. 1.

Next, as shown in FIG. 1-(b), a power supply layer 5 as a platingelectrode is formed, by sputtering method, on whole surfaces of theelectrode layer (electrode pad) 3 and the organic insulation film 4 onthe semiconductor substrate 1.

Next, a photo resist layer 6 is applied on the power supply layer 5 by aspin coating method and exposure, developing and curing processes areperformed, so that, as shown in FIG. 1-(c), the opening corresponding tothe expected forming position on the electrode layer 3 of the solderingbump 9 is formed in the photo resist layer 6.

Next, an electrolytic plating process is performed, so that, as shown inFIG. 1-(d), a barrier metal layer 7 is formed in the opening in thephoto resist layer 6 so that the diffusion of solder in the solderinglayer 9 into the electrode layer is prevented.

Next, an electrolytic plating process is made by using the photo resistlayer 6 as a mask, so that, as shown in FIG. 1-(e), a tin-silver (Sn—Ag)soldering layer 9 is formed on the barrier metal layer 7. At this time,the soldering layer 9 is formed so as to extend on the photo resistlayer 6.

Next, as shown in FIG. 1-(f), the photo resist layer 6 is removed byusing release liquid. Furthermore, an unnecessary part of the powersupply layer 5 is removed by wet etching wherein the soldering layer 9is used as an etching mask.

After that, the soldering layer 9 is made molten by reflow heating sothat, as shown in FIG. 1-(g), the soldering layer 9 is formed in asubstantially spherical shape. In other words, a spherical-shapedsoldering bump (soldering ball) 9 is formed on the electrode layer 3 ofthe semiconductor substrate 1.

In a case where the bump is manufactured by using the printing method,after the barrier metal layer 7 is selectively formed in the opening inthe photo resist 6 shown in FIG. 1-(d), as shown in FIG. 2-(a), thephoto resist layer 6 is removed by using the release liquid and the wetetching process using the etching liquid is applied to the power supplylayer 5.

After that, as shown in FIG. 2-(b), a pattern (not illustrated) forprinting is made so that the tin-silver (Sn—Ag) soldering layer 9 isformed on the barrier metal layer 7, and the soldering plating layer 9is made molten by reflow heating. As a result of this, as shown in FIG.1-(g), the spherical-shaped soldering bump (soldering ball) 9 is formedon the electrode layer 3 of the semiconductor substrate 1.

An example of a method of mounting the semiconductor element 10 wherethe bump 9 made of tin-silver (Sn—Ag) soldering is formed on thesemiconductor substrate 1, on the printed board 11 is shown in FIG. 3.

As shown in FIG. 3-(a), the semiconductor element 10 where the bump 9 isformed on the semiconductor substrate 1 is mounted on the printed board11 by a flip chip bonding method. In other words, where the surface ofthe semiconductor element 10 has the bump 9 formed facing downward, thesemiconductor element 10 is mounted on an upper surface, namely a wiringsurface of the printed board 11. Here, ball bumps 12 for outsideinput/output are formed on a lower surface of the printed board 11

Next, as shown in FIG. 3-(b), in order to improve connectionreliability, underfill 13 is applied between the semiconductor element10 and the printed board 11 and cured, so that connection between thesemiconductor element 10 and the printed board 11 is reinforced.

Last, as shown in FIG. 3-(c), a passive element 14 such as a condenseror the like is provided in the periphery of the semiconductor element 10on the printed board 11 and a heat radiation plate 15 for radiating heatgenerated by the semiconductor element 10 is provided at an upper partof the semiconductor element 10, so that the semiconductor device isformed.

In the meantime, details of forming of the power supply layer 5 on theelectrode layer (electrode pad) 3 and the organic insulation film 4discussed with reference to FIG. 1-(b) and details of the wet etchingprocess for the power supply layer 5 discussed with reference to FIG.1-(f) and FIG. 2-(a) are discussed with reference to FIG. 4 through FIG.6.

Here, FIG. 4 is a view for explaining an electrode layer (electrode pad)and a power supply layer on an organic insulating protection film. FIG.5 is a view for explaining the status of a surface of the organicinsulating protection film in processes shown in FIG. 4. FIG. 6 is aview for explaining the status of a surface of the organic insulatingprotection film in a process for removing the power supply layer by awet etching process.

In order to form the power supply layer 5 on the electrode layer(electrode pad) 3 and the organic insulation film 4, first, as shown inFIG. 4-(a), a dry etching (RF etching) process is applied to the wholesurfaces of the electrode layer (electrode pad) 3 and the organicinsulation film 4 by using argon (Ar) gas so that a natural oxide filmon the surface of the electrode layer (electrode pad) 3 is removed.

By such a dry etching process, as shown in FIG. 5-(a), a modified layeris generated on a surface layer of the organic insulation film 4. Theetching amount of the surface of the organic insulation film 4 at thistime is small and the maximum surface roughness of the organicinsulation film 4 is approximately 4 nm. Therefore, the surfaceroughness of the organic insulation film 4 is not dramatically changedby this process.

Next, a metal forming the power supply layer 5 is deposited on thesurface of the organic insulation film 4 including the modified layer 20by sputtering.

More specifically, as shown in FIG. 4-(b), a titanium (Ti) layer 5-1 isformed on a surface of the organic insulation film 4 including themodified layer 20 by sputtering. By such a sputtering, as shown in FIG.5-(b), titanium is embedded in the surface of the modified layer 20.

Next, as shown in FIG. 4-(c), a copper (Cu) film 5-2 is formed on thesurface of the titanium (Ti) film by sputtering. At this time, as shownin FIG. 5-(c), since the copper film 5-2 is deposited on the titaniumfilm 5-1, the copper film 5-2 does not directly come in contact with theorganic insulation film 4 and therefore does not influence the surfaceof the organic insulation film 4.

In the process shown in FIG. 1-(f) in the case of the plating method orin the process shown in FIG. 2-(a) in the case of the printing method,the power supply layer 5 (the titanium film 5-1 and the copper film 5-2)formed on the organic insulation film 4 is removed by the wet etchingprocess.

Next, with reference to FIG. 6, the status of the surface of the organicinsulation film 4 in the process whereby the power supply layer 5 isremoved by the wet etching process is discussed.

Where the copper film 5-2 is deposited on the titanium film 5-1 as shownin FIG. 6-(a), first, the copper film 5-2 is removed by wet etching asshown in FIG. 6-(b). Since the copper film 5-2 is deposited on thetitanium film 5-1, it is possible to easily remove the copper film 5-2.

Next, as shown in FIG. 6-(c), the titanium film 5-1 deposited on themodified layer 20 is removed by wet etching. While the titanium film 5-1provided on the surface of the modified layer 20 is easily removed,titanium embedded in the surface of the modified layer 20 remains evenafter the titanium film 5-1 provided on the surface of the modifiedlayer 20 is removed.

FIG. 7 is a view of the soldering bump 9 formed on the semiconductorelement 10 of the semiconductor device manufactured by the related artmanufacturing method including the above-discussed processes. FIG. 7-(b)is an expanded view of a part surrounded by a broken line in FIG. 7-(a).

Referring to FIG. 7, in the semiconductor element 10 manufactured by theabove-discussed processes, the titanium film 5-1, the copper film 5-2and the barrier metal layer 7 are formed on the organic insulation film4 in this order. The bump 9 is formed on the barrier metal layer 7.

Titanium 5-1 embedded in the surface of the organic insulation film 4and remaining as a metal residue is normally not observed by a metalmicroscope, an electron microscope, or the like. However, approximately10 atm % of this titanium 5-1, as a maximum, is detected by analysisusing X-ray Photoelectron Spectroscopy (XPS). The surface roughness ofthe organic insulation film 4 is approximately 4 nm as a maximum, whichis substantially equal to the surface roughness of the organicinsulation film 4 formed on the inorganic insulation film 2 shown inFIG. 1-(a).

Thus, in the semiconductor device manufactured by the related artmethod, the titanium 5-1 forming the power supply layer 5 remainsembedded in the surface of the organic insulation film 4 of thesemiconductor element 10 as the metal residue.

However, such a metal residue obstructs adhesion between the organicinsulation film 4 and the underfill 13 (See FIG. 3) filling in betweenthe semiconductor element 10 and the printed board 11 for reinforcingthe connection between the semiconductor element 10 and the printedboard 11. As a result, the reliability of the connection between thesemiconductor element 10 and the printed board 11 after thesemiconductor element 10 is mounted on the printed board 11 may bedegraded.

On the other hand, as discussed above, the surface roughness of theorganic insulation film 4 is approximately 4 nm as a maximum, which issubstantially equal to the surface roughness of the organic insulationfilm 4 formed on the inorganic insulation film 2. Therefore, the surfaceroughness of the organic insulation film 4 is too small to obtainsufficient adhesion with the underfill 13.

Accordingly, the reliability of the connection between the semiconductorelement 10 and the printed board 11 after the semiconductor element 10is mounted on the printed board 11 may be degraded.

Thus, in order to ensure a reliable connection between the semiconductorelement 10 and the printed board 11 after the semiconductor element 10is mounted on the printed board 11, it is necessary to both remove themetal residue remaining embedded in the surface of the organicinsulation film 4 and make the surface roughness of the organicinsulation film 4 large so that sufficient adhesion with the underfill13 can be obtained.

If the organic insulation film 4 in the vicinity of the bump 9 isremoved for the above-mentioned purpose, when the semiconductor element10 is mounted on the printed board 11, stress is concentrated on theorganic insulation film 4 in the vicinity of the bump 9. As a result,cracks may be generated in this part, and therefore the reliability ofthe connection between the semiconductor element 10 and the printedboard 11 after the semiconductor element 10 is mounted on the printedboard 11 may be degraded.

SUMMARY OF THE INVENTION

Accordingly, the present invention may provide a novel and usefulsemiconductor device and manufacturing method of the same solving one ormore of the problems discussed above.

Another and more specific object of the present invention may be toprovide a semiconductor device whereby sufficient adhesion between anorganic insulation film of a semiconductor element and an underfill canbe obtained and concentration of a stress in the organic insulation filmin the vicinity of a bump can be avoided so that reliability ofconnection between the semiconductor element and a printed circuit boardwhere the semiconductor element is mounted can be improved, and amanufacturing method of said semiconductor device.

The above object of the present invention is achieved by a semiconductordevice, including:

a plurality of electrode layers provided at designated positions of asemiconductor substrate;

an organic insulation film formed on the semiconductor substrate byselectively exposing designated areas of the electrode layers; and

projection electrodes for outside connection, the projection electrodesbeing formed on the designated areas of the electrode layers;

wherein thickness of the organic insulation film situated in thevicinity of the periphery of the projection electrodes is greater thanthickness of the organic insulation film situated between the projectionelectrodes.

The above object of the present invention is also achieved by amanufacturing method of a semiconductor device,

the semiconductor device including

electrode layers provided at designated positions of a semiconductorsubstrate;

an organic insulation protection film continuously covering a gapbetween the neighboring electrode layers so that substantially centersof the electrode layers are exposed; and

projection electrodes for outside connection, the projection electrodesbeing connected to the electrode layers;

the manufacturing method including the step of:

etching a surface of the organic insulation protection film by a dryetching process after the projection electrode is formed on theelectrode layer.

According to an embodiment of the present invention, it is possible toprovide the semiconductor device whereby sufficient adhesion between theorganic insulation film of the semiconductor element and the underfillcan be obtained and concentration of the stress in the organicinsulation film in the vicinity of the bump can be avoided so thatreliability of connection between the semiconductor element and theprinted circuit board where the semiconductor element is mounted can beimproved, and the manufacturing method of said semiconductor device.

Other objects, features, and advantages of the present invention will become more apparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view for explaining a plating bump process by using arelated art manufacturing method of a semiconductor device;

FIG. 2 is a view for explaining a forming process of the bump by using aprinting method in the related art manufacturing method of thesemiconductor device;

FIG. 3 is a view showing an example of a method for mounting thesemiconductor element having the bump on the printed circuit board;

FIG. 4 is a view for explaining an electrode layer (electrode pad) and apower supply layer on an organic insulating protection film;

FIG. 5 is a view for explaining the status of a surface of the organicinsulating protection film in processes shown in FIG. 4;

FIG. 6 is a view for explaining the status of a surface of the organicinsulating protection film in a process for removing the power supplylayer by a wet etching process;

FIG. 7 is a view of the bump formed on the semiconductor element of thesemiconductor device manufactured by the related art manufacturingmethod;

FIG. 8 is a view (part 1) showing a forming process of the solder bumpby a plating method in a manufacturing method of a semiconductor deviceof a first embodiment of the present invention;

FIG. 9 is a view (part 2) showing the forming process of the solder bumpby the plating method in the manufacturing method of the semiconductordevice of the first embodiment of the present invention;

FIG. 10 is a view of the bump formed on the semiconductor element of thesemiconductor device manufactured by the manufacturing method of thefirst embodiment of the present invention;

FIG. 11 is a view (part 1) showing a forming process of the solder bumpby a plating method in a manufacturing method of a semiconductor deviceof a second embodiment of the present invention;

FIG. 12 is a view (part 2) showing the forming process of the solderbump by the plating method in the manufacturing method of thesemiconductor device of the second embodiment of the present invention;

FIG. 13 is an expanded view of a part surrounded by a broken line inFIG. 12;

FIG. 14 is a view of the bump formed on the semiconductor element of thesemiconductor device manufactured by the manufacturing method of thesecond embodiment of the present invention; and

FIG. 15 is a view showing a picture of the bump formed on thesemiconductor element of the semiconductor device manufactured by themanufacturing method of the second embodiment of the present invention,taken by a Scanning Electron Microscope (SEM).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description is given below, with reference to the FIG. 8 through FIG.15 of embodiments of the present invention.

First Embodiment

A forming process of a soldering bump by using a plating method of amanufacturing method of a semiconductor device of a first embodiment ofthe present invention, is discussed with reference to FIG. 8 and FIG. 9.

Here, FIG. 8 is a view (part 1) showing a forming process of the solderbump by a plating method in a manufacturing method of a semiconductordevice of a first embodiment of the present invention. FIG. 9 is a view(part 2) showing the forming process of the solder bump by the platingmethod in the manufacturing method of the semiconductor device of thefirst embodiment of the present invention.

In the forming process of the soldering bump by using the plating methodof the manufacturing method of a semiconductor device of a firstembodiment of the present invention, as shown in FIG. 8-(a), anelectrode layer (electrode pad) 33 made of aluminum (Al) or the like isprovided on an upper surface of a semiconductor substrate 31 made ofsilicon (Si). In addition, an inorganic insulation film (passivationfilm) 32 made of silicon nitride (SiN) or the like is formed in theperiphery of the electrode layer 33.

In addition, an organic insulation film 34 such as a polyimide resinlayer or the like is provided on the inorganic insulation film 32. Theorganic insulation film 34 is formed for surface protection of thesemiconductor element and for easing stress concentrated on a base ofthe bump 39 when the semiconductor element is mounted on a wiring board11 (See FIG. 3).

An opening is formed in the inorganic insulation film 32 and the organicinsulation film 34 as corresponding to an expected forming position onthe electrode layer 33 of the soldering bump 39 so that a pad isexposed.

Illustration of an active element such as a transistor, and a passiveelement such as resistor element or capacity element formed on thesemiconductor substrate 31, an isolation area for insulation-isolatingbetween these elements, an interlayer insulation layer, an inter-elementmutual wiring layer, or the like is omitted in FIG. 8 and FIG. 9.

Next, as shown in FIG. 8-(b), a power supply layer 35 as a platingelectrode is formed on whole surfaces of the electrode layer (electrodepad) 33 and the organic insulation film 34 provided on the semiconductorsubstrate 31.

In order to form the power supply layer 35 on the electrode layer(electrode pad) 33 and the organic insulation film 34, a dry etching (RFetching) process using argon (Ar) gas is applied so that a natural oxidefilm on the surface of the electrode layer (electrode pad) 33 isremoved.

As discussed above, by such a dry etching process, a modified layer (notshown) is generated on a surface of the organic insulation film 34.

After that, a titanium (Ti) layer 35-1 (See FIG. 10) is formed on thesurface of the organic insulation film 34 by sputtering. By such asputtering, titanium is embedded in the surface of the modified layer onthe surface of the organic insulation film 34.

Next, a copper (Cu) film 35-2 is formed on the surface of the titanium(Ti) film 35-1 by sputtering. At this time, since the copper film 35-2is deposited on the titanium film 35-1, the copper film 35-2 does notdirectly come in contact with the organic insulation film 34 andtherefore does not influence the surface of the organic insulation film34.

Next, photo resist is applied on the power supply layer 35 by a spincoating method and exposure, developing and curing processes areperformed, so that, as shown in FIG. 8-(c), the photo resist layer 36having the opening pattern corresponding to the expected formingposition on the electrode layer 33 of the soldering bump 39 is formed.

Next, an electrolytic plating process is performed, so that, as shown inFIG. 8-(d), a barrier metal layer 37 is formed in the opening in thephoto resist layer 36 so that the diffusion of solder in the solderinglayer is prevented.

Next, an electrolytic plating process is performed by using the photoresist layer 36 as a mask, so that, as shown in FIG. 8-(e), a tin-silver(Sn—Ag) soldering layer 39 is formed on the barrier metal layer 37. Atthis time, the soldering layer 39 is formed so as to extend on the photoresist layer 36.

Next, as shown in FIG. 8-(f), the photo resist layer 36 is removed byusing release liquid. Furthermore, as shown in FIG. 9-(g), anunnecessary part of the power supply layer 35 is removed by wet etchingwherein the soldering layer 39 is used as an etching mask.

After that, the soldering layer 39 is made molten by reflow heating sothat, as shown in FIG. 9-(h), the soldering layer 39 is shaped in asubstantially spherical shape. In other words, a spherical-shapedsoldering bump (soldering ball) 39 as a projection electrode for outsideconnection is formed on the electrode layer 33 of the semiconductorsubstrate 31.

In this embodiment, after the soldering bump (soldering ball) 39 iscompletely formed, as shown in FIG. 9-(i), the surface of the organicinsulation film 34 is etched by a dry etching process. In addition, inthis embodiment, the surface of the organic insulation film 34 is etchedby a dry etching process using radio frequency (RF) plasma etching orthe like.

In a process using a down flow type apparatus generally used for etchingthe surface of an organic insulation film, it is difficult to etch thesurface of the organic insulation film where the soldering bump isformed. Mixed gas of oxygen (O₂) and carbon tetrafluoride (CF₄) may beused for such a dry etching process. In this case, for example, the dryetching process may be performed for approximately 45 seconds under aradio frequency plasma atmosphere of approximately 150 W under theconditions that the flow amount of oxygen (O₂) is approximately 400 sccmand the flow amount of carbon tetrafluoride (CF₄) is approximately 100sccm.

However, the flow amounts of the mixed gas are not limited to theabove-mentioned example. For example, the mixture ratio of the two gasesmay be the same while the flow amounts of both gases are changed. Inaddition, the material for the gas is not limited to the above-mentionedexample. For example, trifluoromethane (CHF₃) gas may be used.

FIG. 10 is a view of the bump formed by the above-discussed processes.FIG. 10-(b) is an expanded view of a part surrounded by a broken line inFIG. 10-(a).

Referring to FIG. 10, the titanium film 35-1, the copper film 35-2 andthe barrier metal layer 37 are formed on from the aluminum electrodelayer (electrode pad) 33 and the organic insulation film 34 in thisorder. The bump 39 as the projection electrode for outside connection isformed on the barrier metal layer 37. The organic insulation film 34continuously covers the surface of the semiconductor element existingbetween the neighboring electrode layers 33.

Here, an organic insulation film on which the power supply layer 35 isnot provided and in an area “A” inside of a point of the externalperiphery of the bump 39 and in a direction parallel to the main surfaceof the semiconductor substrate 31, that is, an organic insulation filmin the vicinity of the bump 39, is called a bump-vicinity organicinsulation film 34-1. An organic insulation film in an area “B”, namelyan area other than area A, is called an etched organic insulation film34-2.

The thickness of the bump-vicinity organic insulation film 34-1, thatis, the distance between the upper surface of the bump-vicinity organicinsulation film 34-1 and a surface of the inorganic insulation film 32coming in contact with the bump-vicinity organic insulation film 34-1,is substantially equal to the distance between the upper surface of theorganic insulation film 34 when covering the inorganic insulation film32 as shown in FIG. 8-(a) and the surface of the inorganic insulationfilm 32 coming in contact with the bump-vicinity organic insulation film34-1.

On the other hand, substantially 50 through 400 nm of the etched organicinsulation film 34-2 is dry etched by the etching process discussed withreference to FIG. 9-(i) so that the etched organic insulation film 34-2is thinner than the bump-vicinity organic insulation film 34-1.

Thus, while the etched organic insulation film 34-2 being thinner thanthe bump-vicinity organic insulation film 34-1 is formed by the dryetching process shown in FIG. 9-(i), the bump-vicinity organicinsulation film 34-1 being thicker than the etched organic insulationfilm 34-2 is provided in the periphery of the bump 39. Therefore, evenif the stress is concentrated on the bump-vicinity organic insulationfilm 34-1 when the semiconductor element is mounted on a wiring board 11(See FIG. 3), it is possible to prevent the generation of cracks at thispart.

In addition, the surface roughness of the bump-vicinity organicinsulation film 34-1 is approximately 4 nm as a maximum, which issubstantially equal to the surface roughness of the organic insulationfilm 34 when the organic insulation film 34 is formed on the inorganicinsulation film 32 as shown in FIG. 8-(a).

On the other hand, the surface roughness of the etched organicinsulation film 34-2 is equal to or greater than 5 times the surfaceroughness of the bump-vicinity organic insulation film 34-1, namelyequal to or greater than approximately 20 nm, by the process shown inFIG. 9-(g).

Therefore, it is possible to obtain sufficient adhesion between theunderfill 13 (See FIG. 3) and the organic insulation film 34 so that thereliability of the connection between the semiconductor element 10 andthe printed board 11 after the semiconductor element 10 is mounted onthe printed board 11 can be secured.

In addition, in the process shown in FIG. 8-(b), when the titanium (Ti)film 35 is formed on the organic insulation film 34 by sputtering afterthe etching process using argon (Ar), titanium (Ti) is embedded in themodified layer situated on the surface of the organic insulation film 34and remains as the metal residue.

According to the analysis using the X-ray Photoelectron Spectroscopy(XPS), 10 atm %, as a maximum, of the metal residue remains in thebump-vicinity organic insulation film 34-1 and only approximately 0.1atm % or less of the metal residue remains in the etched organicinsulation film 34-2 because the metal residue is removed together withthe organic insulation film 34 by the process shown in FIG. 9-(g).

Thus, since almost all of the metal residue is removed from the etchedorganic insulation film 34-2, it is possible to obtain sufficientadhesion between the underfill 13 and the organic insulation film 34 sothat the reliability of the connection between the semiconductor element10 and the printed board 11 after the semiconductor element 10 ismounted on the printed board 11 can be secured.

According to the first embodiment of the present invention, the etchedorganic insulation film 34-2 whose surface roughness is greater than thesurface roughness of the bump-vicinity organic insulation film 34-1 isformed by the dry etching process shown in FIG. 9-(i), and the metalresidue embedded in the surface of the organic insulation film 34-2 isremoved by the process shown in FIG. 9-(i).

On the other hand, the thickness of the bump-vicinity organic insulationfilm 34-1 is not changed from the thickness of the organic insulationfilm 34 when the organic insulation film 34 is formed on the inorganicinsulation film 32 as shown in FIG. 8-(a). Therefore, the strength inthe vicinity of the bump 39 is not reduced.

Thus, according to the first embodiment of the present invention, it ispossible to obtain sufficient adhesion between the underfill 13 and theorganic insulation film 34 and avoid concentration of stress on thebump-vicinity organic insulation film 34-1 in the vicinity of the bum39, so that the reliability of the connection between the semiconductorelement 10 and the printed board 11 after the semiconductor element 10is mounted on the printed board 11 can be secured.

In the first embodiment of the present invention, a case where the bumpis formed by the plating method is discussed. However, the presentinvention is not limited to this. For example, the bump shown in FIG. 10can be formed by dry etching the surface of the organic insulation film37 as shown in FIG. 9-(i) in a case where the bump is formed by using atransferring bump method, paste bump method, or screen printing method.

In addition, tin-silver (Sn—Ag) is used as an example of bump materialin the first embodiment of the present invention. However, the bumpmaterial is not limited to this. For example, tin-silver-copper(Sn—Ag—Cu), tin-bismuth (Sn—Bi), tin-lead (Sn—Pb), or the like may beused as the bump material.

Second Embodiment

A forming process of a soldering bump by using a plating method of amanufacturing method of a semiconductor device of a second embodiment ofthe present invention, is discussed with reference to FIG. 11 throughFIG. 13.

Here, FIG. 11 is a view (part 1) showing a forming process of the solderbump by a plating method in a manufacturing method of a semiconductordevice of a second embodiment of the present invention. FIG. 12 is aview (part 2) showing the forming process of the solder bump by theplating method in the manufacturing method of the semiconductor deviceof the second embodiment of the present invention. FIG. 13 is anexpanded view of a part surrounded by a broken line in FIG. 12.

In the forming process of the soldering bump by using the plating methodof the manufacturing method of a semiconductor device of a firstembodiment of the present invention, as shown in FIG. 11-(a), anelectrode layer (electrode pad) 43 made of aluminum (Al) or the like isprovided on an upper surface of a semiconductor substrate 41 made ofsilicon (Si). In addition, an inorganic insulation film (passivationfilm) 42 made of silicon nitride (SiN) or the like is formed in theperiphery of the electrode layer 43.

In addition, an organic insulation film 44 such as a polyimide resinlayer or the like is provided on the inorganic insulation film 42. Theorganic insulation film 44 is formed for surface protection of thesemiconductor element and for easing stress concentrated on a base ofthe bump 49 when the semiconductor element is mounted on a wiring board41 (See FIG. 3).

An opening is formed in the inorganic insulation film 42 and the organicinsulation film 44 as corresponding to an expected forming position onthe electrode layer 43 of the soldering bump 49 so that a pad isexposed.

Illustration of an active element such as a transistor, and a passiveelement such as resistor element or capacity element formed on thesemiconductor substrate 41, an isolation area for insulation-isolatingbetween these elements, an interlayer insulation layer, an inter-elementmutual wiring layer, or the like is omitted in FIG. 11 through FIG. 13.

Next, as shown in FIG. 11-(b), a power supply layer 45 as a platingelectrode is formed on whole surfaces of the electrode layer (electrodepad) 43 and the organic insulation film 44 provided on the semiconductorsubstrate 41.

In order to form the power supply layer 45 on the electrode layer(electrode pad) 43 and the organic insulation film 44, a dry etching (RFetching) process using argon (Ar) gas is applied so that a natural oxidefilm on the surface of the electrode layer (electrode pad) 43 isremoved.

As discussed above, by such a dry etching process, a modified layer (notshown) is generated on the surface of the organic insulation film 44.

After that, a titanium (Ti) layer 45-1 (See FIG. 14) is formed on thesurface of the organic insulation film 44 by sputtering. By such asputtering, titanium is embedded in the surface of the modified layer onthe surface of the organic insulation film 44.

Next, a copper (Cu) film 45-2 (See FIG. 14) is formed on the surface ofthe titanium (Ti) film 45-1 by sputtering. At this time, since thecopper film 45-2 is deposited on the titanium film 45-1, the copper film45-2 does not directly come in contact with the organic insulation film44 and therefore does not influence the surface of the organicinsulation film 44.

Next, photo resist is applied on the power supply layer 45 by a spincoating method and exposure, developing and curing processes areperformed, so that, as shown in FIG. 11-(c), the photo resist layer 46having the opening pattern corresponding to the expected formingposition on the electrode layer 43 of the soldering bump 49 is formed.

Next, an electrolytic plating process is performed, so that, as shown inFIG. 11-(d), a barrier metal layer 47 is formed in the opening in thephoto resist layer 36 so that the diffusion of solder in the solderinglayer is prevented.

Next, an electrolytic plating process is performed by using the photoresist layer 46 as a mask, so that, as shown in FIG. 11-(e), atin-silver (Sn—Ag) soldering layer 49 is formed on the barrier metallayer 47. At this time, the soldering layer 49 is formed so as to extendon the photo resist layer 46.

Next, as shown in FIG. 11-(f), the photo resist layer 46 is removed byusing release liquid.

Furthermore, as shown in FIG. 12-(g), an unnecessary part of the powersupply layer 45 is removed by a wet etching wherein the soldering layer49 is used as an etching mask.

In this embodiment, after the power supply layer 45 is removed by thewet etching process, as shown in FIG. 12-(h), the dry etching process isapplied so that the surface of the organic insulation layer 44 ismodified.

More specifically, the surface of the organic insulation film 44 is dryetched by radio frequency (RF) plasma using nitrogen (N₂) as gas. As aprocess condition, for example, the flow amount of the nitrogen gas isapproximately 500 sccm and the power of the radio frequency (RF) plasmais approximately 400 W.

Gas used in this process is not limited to nitrogen (N₂) gas. Forexample, argon (Ar) gas may be used.

By such a plasma process, surface bonding in an area not covered withthe soldering layer 49 in a surface of the organic insulation film 44becomes strong (tight). As a result of this, the surface is modified sothat it may be difficult to apply the dry etching process using mixedgas of oxygen (O₂) and carbon tetrafluoride (CF₄). Such a modified partis indicated by numerical reference “50” in FIG. 12-(h)

On the other hand, no influence of the dry etching process is given to apart not contacting the plasma and shaded by the soldering layer 49 onthe surface of the organic insulation film 44 so that this part is notmodified.

In the plasma process shown in FIG. 12-(h), the surface of the organicinsulation film 44 is mostly not etched. Even if the surface of theorganic insulation film 44 is etched, the etched amount is equal to orless than several nm. In addition, the surface roughness of the organicinsulation film 44 is mostly not changed. The surface roughness of theorganic insulation film 44 is approximately 4 nm as a maximum, which issubstantially equal to the surface roughness of the organic insulationfilm 44 in a state where the organic insulation film 44 is formed on theinorganic insulation film 42 shown in FIG. 11-(a).

Influence of the nitrogen gas is given to the vicinity of a border of anexposed area not shaded by the soldering layer 49 and the area shade bythe soldering layer 49 on the surface of the organic insulation film 44.Hence, as compared with the exposed area not shaded by the solderinglayer 49, the surface of the vicinity of the border is modified whilemodified thickness is thin.

After the surface of the organic insulation film 47 is modified by theabove-mentioned plasma process, as shown in FIG. 12-(i), the solderinglayer 49 is formed in a substantially spherical shape by reflow heating.

In other words, a spherical-shaped soldering bump (soldering ball) 49 isformed on the electrode layer 43 of the semiconductor substrate 41 byreflow heating.

The diameter of the spherical soldering bump (soldering ball) 49 formedin the substantially spherical shape by reflow heating is smaller thanthe diameter of the soldering layer 49 formed by the electrolyticplating process shown in FIG. 11-(e). Therefore, a part not modified bythe plasma process shown in FIG. 12-(h) of the organic insulation film44 is exposed.

Next, as shown in FIG. 12-(i), the surface of the organic insulationfilm 44 is etched by the dry etching process.

As well as the first embodiment of the present invention, the radiofrequency (RF) plasma etching using mixed gas of oxygen (O₂) and carbontetrafluoride (CF₄) is applied as this dry etching process. In thiscase, while the flow amount of the gas may be substantially same as theflow amount of gas used in the first embodiment of the present invention(that is, the flow amount of oxygen (O₂) is approximately 400 sccm andthe flow amount of carbon tetrafluoride (CF₄) is approximately 100sccm), the power of the radio frequency (RF) plasma is greater than theplasma power used in the first embodiment of the present invention andis equal to approximately 400 W. Under the above-mentioned conditions,the dry etching process is performed for approximately 30 seconds, forexample.

The flow amount of the mixed gas is not limited to the above-mentionedexample. For example, the mixture ratio of the two gases may be the samewhile the flow amounts of both gases are changed. In addition, thematerial for the gas is not limited to the above-mentioned example. Forexample, trifluoromethane (CHF₃) gas may be used.

FIG. 13 is an expanded view of a part surrounded by a broken line inFIG. 12.

In FIG. 13-(a), a part indicated by a broken line A is a surface area ofthe organic insulation film 44 that is modified by the plasma processusing the nitrogen gas (N₂) in the process shown in FIG. 12-(h) so thatthe surface bonding becomes strong (tight).

In FIG. 13-(a), a part indicated by a broken line B is a surface area ofthe organic insulation film 44 that is not modified because the surfaceis shaded by the soldering layer 49 and is not influenced by the plasmaso that the surface remains soft.

In FIG. 13-(a), a part indicated by a broken line C is a surface area ofthe organic insulation film 44 that is in the vicinity of a border of anexposed area not shaded by the soldering layer 49 and the area shade bythe soldering layer 49. As compared with the exposed area not shaded bythe soldering layer 49, this surface in the vicinity of the border ismodified and becomes strong (tight) due to the influence of the nitrogengas at the time of the plasma process while the thickness of themodified part is made thin.

Because of this, the etching rate of the radio frequency (RF) plasmaetching using the mixed gas of oxygen (O₂) and carbon tetrafluoride(CF₄) is faster to slower in the order of the part indicated by thebroken line B, the broken line C, and the broken line A.

Accordingly, as shown in FIG. 13-(b), the part indicated by the brokenline B, namely an area where no influence of the plasma is given so thatno modification is made and the area remains soft, has an etched rategreater than the part indicated by the broken line A, namely an areawhere influence of the plasma is given so that the modification is madeand the area becomes tight. Therefore the part indicated by the brokenline B is deeply etched.

FIG. 14 is a view of the bump formed by the above-discussed processes.FIG. 14-(b) is an expanded view of a part surrounded by a dotted line inFIG. 14-(a).

Referring to FIG. 14, the titanium film 45-1, the copper film 45-2 andthe barrier metal layer 47 are stacked on the aluminum electrode layer(electrode pad) 43 and the organic insulation film 44 in this order. Thebump 49 as the projection electrode for outside connection is formed onthe barrier metal layer-47. The organic insulation film 44 continuouslycovers the surface of the semiconductor element existing between theneighboring electrode layers 43.

In the following explanation, an organic insulation film on which thepower supply layer 45 is not provided and in an area “X” inside of apoint of the external periphery in a direction parallel to the mainsurface of the semiconductor substrate 41, is called a bump-vicinityorganic insulation film 44-1.

An organic insulation film formed in an area Y being deeply etched bythe dry etching shown in FIG. 12-(j), as shown in FIG. 13-(b), (“a firstarea” in claims) is called a first etched organic insulation film 44-2.

An organic insulation film formed in an area Z outside of the area Y (“asecond area” in claims) is called a second etched organic insulationfilm 44-3.

Thickness of the bump-vicinity organic insulation film 44-1, that is,the distance between the surface of the bump-vicinity organic insulationfilm 44-1 and a surface of the inorganic insulation film 42 coming incontact with the bump-vicinity organic insulation film 44-1, issubstantially equal to the distance between the surface of the organicinsulation film 44 when covering the inorganic insulation film 42 asshown in FIG. 11-(a) and the surface of the inorganic insulation film 42coming in contact with the bump-vicinity organic insulation film 44-1.

On the other hand, approximately 600 nm of the first etched organicinsulation film 44-2 is dry etched by the etching process discussed withreference to FIG. 12-(j) and approximately 50 through 200 nm of thesecond etched organic insulation film 44-3 is dry etched by the etchingprocess discussed with reference to FIG. 12-(j), so that the firstetched organic insulation film 44-2 is thinner than the second etchedorganic insulation film 44-3.

Therefore, while the part being thinner than the bump-vicinity organicinsulation film 44-1 is formed by the dry etching process shown in FIG.12-(j), the bump-vicinity organic insulation film 44-1 being thickerthan the part is provided in the periphery of the bump 39. Therefore,even if the stress is concentrated on the bump-vicinity organicinsulation film 44-1 when the semiconductor element is mounted on awiring board 11 (See FIG. 3), it is possible to prevent the generationof the cracks at this part.

In addition, the surface roughness of the second etched organicinsulation film 44-3 by the dry etching process shown in FIG. 12-(j) isapproximately 100 nm as a maximum, which is equal to or approximatelyfive times the surface roughness of the bump-vicinity organic insulationfilm 44-1

Therefore, it is possible to obtain sufficient adhesion between theunderfill 13 and the organic insulation film 44 so that the reliabilityof the connection between the semiconductor element 10 and the printedboard 11 after the semiconductor element 10 is mounted on the printedboard 11 can be secured.

In a process shown in FIG. 11-(b), the titanium (Ti) film 45-1 (See FIG.14) is formed on the surface of the organic insulation protection film44 by sputtering so that the titanium (Ti) is embedded in and remains inthe surface as a metal residue. While approximately 10 atm %, as amaximum, of the metal residue remain in the bump-vicinity organicinsulation film 44-1, almost all of the metal residue in the etchedorganic insulation film 44-2 is removed by the process shown in FIG.12-(j) and therefore approximately 0.1 atm % or less of the metalresidue remains embedded in the etched organic insulation film 44-2.

Thus, in the etched organic insulation film 44-2, almost all of themetal residue is removed. Hence, it is possible to obtain sufficientadhesion between the underfill 13 and the organic insulation film 44 sothat the reliability of the connection between the semiconductor element10 and the printed board 11 after the semiconductor element 10 ismounted on the printed board 11 can be secured.

An inventor of the present invention took a picture of the bumpstructure of the second embodiment of the present invention by using aScanning Electron Microscope (SEM). The picture is shown in FIG. 15.

FIG. 15-(a) is a picture where the bump is removed from the bumpstructure of the second embodiment of the present invention. FIG. 15-(b)is a cross-sectional structure of FIG. 15-(a). Referring to FIG. 15-(a),it is found that the bump-vicinity organic insulation film 44-1, thefirst etched organic insulation film 44-2, and the second etched organicinsulation film 44-3 are formed, in this order, in the periphery of apart where the soldering bump 49 is provided.

The inventor of the present invention also found that the surfaceroughness of the bump-vicinity organic insulation film 44-1 is equal toor greater than 1.5 nm and equal to or less than 3.7 nm, the surfaceroughness of the first etched organic insulation film 44-2 is equal toor greater than 9.8 nm and equal to or less than 16.2 nm, and thesurface roughness of the second etched organic insulation film 44-3 isequal to or greater than 31.5 nm and equal to or less than 48.3 nm.Thus, it is found that the surface roughness of the second etchedorganic insulation film 44-3 is sufficiently greater than the surfaceroughness of the bump-vicinity organic insulation film 44-1.

Furthermore, referring to FIG. 15-(b), the inventor of the presentinvention found that while no influence by the etching is given to thesurface of the bump-vicinity organic insulation film 44-1, approximately500 through 600 nm of the first etched organic insulation film 44-2 isetched and approximately 50 through 200 nm of the second etched organicinsulation film 44-3 is etched. Thus, it is found that the first etchedorganic insulation film 44-2 is thinner than the second etched organicinsulation film 44-3, and the second etched organic insulation film 44-3is thinner than the bump-vicinity organic insulation film 44-1.

According to the second embodiment of the present invention, the etchedorganic insulation films 44-2 and 44-3, each of whose surface roughnessis greater than the surface roughness of the bump-vicinity organicinsulation film 44-1, are formed by the dry etching process shown inFIG. 12-(j), and the metal residue embedded in the surfaces of theetched organic insulation films 44-2 and 44-3 is removed by the processshown in FIG. 11-(b).

In addition, the surface of the organic insulation film 44 is modifiedby applying the dry etching process shown in FIG. 12-(h), and then thedry etching process shown in FIG. 12-(j) is applied. Therefore, a partof the organic insulation film 44 is deeply etched so that the firstetched organic protection film 44-2 is made.

On the other hand, the thickness of the bump-vicinity organic insulationfilm 44-1 is not changed from the thickness of the organic insulationfilm 44 when the organic insulation film 44 is formed on the inorganicinsulation film 42 as shown in FIG. 11-(a). Therefore, the strength inthe vicinity of the bump 49 is not reduced.

Hence, sufficient adhesion between the organic insulation film 44 andthe underfill 13 can be obtained and concentration of the stress in theorganic insulation film 44-1 in the vicinity of the bump 49 can beavoided, so that reliability of connection between the semiconductorelement and a printed circuit board where the semiconductor element ismounted can be improved.

According to a Pressure Cooker Test (PCT) under the conditions that thetemperature is 121° C. and the moisture is 85%, while the organicinsulation film is removed from the underfill after 168 hours havepassed in the semiconductor device having a related art structure shownin FIG. 7, the adhesion between the organic insulation film and theunderfill is maintained even after 168 hours are passed in thesemiconductor device of the present invention.

In addition, it is found that, according to the Pressure Cooker Test(PCT) after the dry etching process is applied so that the metal residuein the surface of the organic insulation film is equal to or less thanapproximately 0.1 atm %, the adhesion between the organic insulationfilm and the underfill is maintained even after 264 hours have passed.

Furthermore, in a case where these are combined, that is, in a casewhere the surface roughness of the organic insulation film is made thesame as in each of the above-discussed embodiments and the dry etchingprocess is applied so that the metal residue in the surface of theorganic insulation film is equal to or less than approximately 0.1 atm%, and then the Pressure Cooker Test is implemented, it is found thatthe adhesion between the organic insulation film and the underfill ismaintained even after 504 hours have passed.

Therefore, according to the present invention, approximately three timesor more reliability as compared to the related art is obtained. Hence,it is possible to provide a semiconductor device having a good adhesionafter the semiconductor element is mounted on the printed board.

Thus, according to the embodiments of the present invention, withoutchanging the thickness of the organic insulation film in the vicinity ofthe bump, by the dry etching process, the surface roughness of theorganic insulation film situated outside of the organic insulation filmin the vicinity of the bump can be made greater than the surfaceroughness of the organic-insulation film in the vicinity of the bump andthe metal residue embedded in the surface can be removed.

Also, according to the embodiments of the present invention, sufficientadhesion between the organic insulation film of the semiconductorelement and the underfill can be obtained and concentration of thestress in the organic insulation film in the vicinity of the bump can beavoided and therefore the strength is maintained, so that reliability ofthe connection between the semiconductor element and a printed circuitboard where the semiconductor element is mounted can be improved.

The present invention is not limited to these embodiments, butvariations and modifications may be made without departing from thescope of the present invention.

This patent application is based on Japanese Priority Patent ApplicationNo. 2005-367210 filed on Dec. 20, 2005, the entire contents of which arehereby incorporated by reference.

1. A semiconductor device, comprising: a plurality of electrode layersprovided at designated positions of a semiconductor substrate; anorganic insulation film formed on the semiconductor substrate byselectively exposing designated areas of the electrode layers; andprojection electrodes for outside connection, the projection electrodesbeing formed on the designated areas of the electrode layers; whereinthickness of the organic insulation film situated in the vicinity of theperiphery of the projection electrodes is greater than thickness of theorganic insulation film situated between the projection electrodes. 2.The semiconductor device as claimed in claim 1, wherein the organicinsulation film situated between the projection electrodes is formed bya first area and a second area situated outside of the first area; andthickness of the first area is less than thickness of the second area.3. The semiconductor device as claimed in claim 1, wherein the thicknessof the organic insulation film situated between the projectionelectrodes is less than the thickness of the organic insulation filmsituated in the vicinity of the periphery of the projection electrodesby approximately 50 through 1000 nm.
 4. The semiconductor device asclaimed in claim 1, wherein surface roughness of the organic insulationfilm situated between the projection electrodes is equal to or greaterthan approximately 5 times the surface roughness of the organicinsulation film situated in the vicinity of the periphery of theprojection electrodes.
 5. The semiconductor device as claimed in claim1, wherein the surface roughness of the organic insulation film situatedbetween the projection electrodes is equal to or greater thanapproximately 20 nm.
 6. The semiconductor device as claimed in claim 1,wherein the projection electrode is connected to the electrode layer viaa metal layer; and an amount of metal forming the metal layer includedin the organic insulation film situated between the projectionelectrodes is smaller than an amount of metal forming the metal layerincluded in the organic insulation film situated in the vicinity of theperiphery of the projection electrode.
 7. The semiconductor device asclaimed in claim 6, wherein the amount of the metal forming the metallayer included in the organic insulation film situated between theprojection electrodes is equal to or smaller than 0.1 atm %.
 8. Amanufacturing method of a semiconductor device, the semiconductor deviceincluding electrode layers provided at designated positions of asemiconductor substrate; an organic insulation protection filmcontinuously covering a gap between the neighboring electrode layers sothat substantially centers of the electrode layers are exposed; andprojection electrodes for outside connection, the projection electrodesbeing connected to the electrode layers; the manufacturing methodcomprising the step of: etching a surface of the organic insulationprotection film by a dry etching process after the projection electrodeis formed on the electrode layer.
 9. The manufacturing method of thesemiconductor device as claimed in claim 8, wherein the dry etchingprocess is a radio frequency (RF) dry etching.
 10. The manufacturingmethod of the semiconductor device as claimed in claim 8, wherein gasused for the dry etching process is mixed gas of oxygen gas, carbontetrafluoride (CF₄) or trifluoromethane (CHF₃)
 11. The manufacturingmethod of the semiconductor device as claimed in claim 8, wherein asurface of the organic insulation protection film is modified before theprojection electrode is formed on the electrode layer.
 12. Themanufacturing method of the semiconductor device as claimed in claim 11,wherein the surface of the organic insulation protection film ismodified by a surface modification dry etching process.
 13. Themanufacturing method of the semiconductor device as claimed in claim 12,wherein the surface modification dry etching process is a radiofrequency (RF) dry etching.
 14. The manufacturing method of thesemiconductor device as claimed in claim 12, wherein nitrogen gas orargon gas is used for the surface modification dry etching process. 15.The manufacturing method of the semiconductor device as claimed in claim12, wherein a layer formed by a material of the projection electrode isprovided on the electrode layer before the surface modification dryetching process is implemented; and the surface modification dry etchingprocess is applied to a part of the surface of the organic insulationprotection film, the part being not covered with the layer formed by thematerial of the projection electrode so as to be exposed, so that thepart is modified.